PARIS, May 19 (Reuters) - One of the few cartoonists to survive an Islamist militant attack on France's Charlie Hebdo journal is leaving the publication, saying he can no longer bear the pressure.

Renald Luzier, better known simply as Luz, announced his decision in an interview in Liberation, the newspaper that has housed Charlie Hebdo and helped it publish since an attack in which most of his cartoonist colleagues were killed.

"The time came when it was just all too much to bear. There was next to nobody to draw the cartoons. I ended up doing three or every four front-pages. Every print-run was torture because the others are no longer there," said Luz.

He drew the cover picture on the first post-attack edition of Charlie Hebdo - which sold some eight million copies across the world compared to a normal week's sales of around 60,000 - but he had recently said he would no longer draw cartoons of the Prophet Mohammad because he was fed up with the matter.

For Muslims, any depiction of the Prophet is blasphemous; but Charlie Hebdo's first post-attack edition carried on its cover a Luz cartoon of a tearful Mohammad holding a "Je suis Charlie" ("I am Charlie") sign under the words "All is forgiven."

NO HERO

Islamist militants saying they were avenging the Prophet killed 12 people in January when they attacked the Paris offices of the irreverent weekly known for lampooning Islam along with other religions and the political establishment. Among those killed were chief editor Stephane Charbonnier and household-name cartoonists such as Georges Wolinski and Jean Cabut.

Luz, who lives under police protection like the rest of the survivors and colleagues at other newspapers such as the Canard Enchaine, cited pressure of work and media scrutiny as the main reasons for quitting.

The ad-free publication overcame serious financial woes thanks to donations since the Jan.7 attack and the massive but temporary post-attack boost to sales for the journal that sells at 3 euros ($3.36) per copy.

Luz said his decision had nothing to do with the problems at the journal, including splits that only recently surfaced over its staff ownership structure and disciplinary proceeedings against one of its journalists.

"I'm no longer interested in returning to normal life as a news cartoonist," said Luz.

He spoke of the fear of no longer being inspired and being fed up with hero status that meant his every move triggered media headlines.

"We're not heroes, we never were and we never wanted to be," he said.

At no point, however, did he speak of fear of being targeted again by militants. ($1 = 0.8940 euros) (Reporting By Brian Love; editing by Ralph Boulton)